The BBC's Charles Scanlon"The World Health Organisation is now turning its attention to India" real 56k

Sunday, 29 October, 2000, 04:32 GMT

Polio milestone passed

Oral polio vaccine has saved millions from the disease

Scientists have announced the eradication of the crippling disease polio from 37 Pacific Rim countries.

And they have dismissed warnings that use of a particular sort of polio vaccine to achieve this increases the risk that the disease could re-emerge.

We have never seen an outbreak caused by this in 30 years

Dr Bruce Aylward, WHO

The World Health Organisation has overseen mass immunisation programmes in countries such as China, Vietnam, Cambodia, and South Korea.

The campaign has had to overcome huge logistical difficulties to reach remote areas with vaccines.

However, a study published in the Lancet medical journal on Friday suggested that the use of "live vaccines" - which contain active but genetically altered copies of the actual polio virus, could mean the illness could return if vaccination efforts stopped.

The live poliovirus vaccine is given by mouth to children, often in the form of a sugarlump or a droplet.

It has long been established that the altered viruses it contains can be replicated in the gut of immunised children, and gradually revert to the form which causes disease.

Indeed, there are a small number of cases of vaccine-induced polio which occur as a result of immunisation programmes.

Sewage system

The Japanese researchers found that children given the vaccine were excreting poliovirus into the sewage system - and that there were detectable levels there.

They believe that this creates a risk that polio, far from being eradicated, could strike again if immunisation ever stops.

The researchers wrote: "There is an environmental risk of vaccine-associated paralytic poliomyelitis as long as live oral poliovirus vaccine is not replaced with inactivated polio vaccine."

However, the WHO is against the universal use of inactivated virus vaccine - in which the virus is rendered completely incapable of replicating - on the grounds that it is less effective than live vaccines.

Dr Bruce Aylward, the coordinator of the programme in Western Pacific region, said that despite the presence of poliovirus in sewage and river water, there had never been a recorded case in which anyone had acquired the virus from this source.

He said: "The study is valuable work, as it helps us put together our strategy for the endgame against polio.

"In Cuba, they found a similar thing was happening, but that the presence of the virus died away naturally shortly afterwards.

"We have never seen an outbreak caused by this in 30 years."

He said that even in countries in which polio had been eradicated, ongoing vigilance was essential to make sure the virus could not come back.

He mentioned one recent case in northwest China which was traced to a long distance trade route between there and a region of India.

"This kind of case is the main threat," he said.

Action Research, a medical research charity that helped fund the development of Britain's first polio vaccine, called for reassurances that the world-wide immunisation programme would not suffer due to concern about the use of 'live vaccines'.

Director John Grounds said: "We cannot yet afford to consider polio a threat of the past.

"We are concerned that speculation regarding the use of 'live vaccines', as with the BSE scare of ten days ago, will result in parents around the world not vaccinating their children against the virus - this is a risk that none of us can afford to take."